Diastereoselective Cyclopropanation of Alkenes with α-Alkyl-α-diazoesters

Significance

Rhodium carbenoids of alkyl-di­azoacetates 1 are not generally used in intermolecular reactions because the easily lead to elimination products 4. This is why most successful Rh-catalyzed reactions of diazoacetates use electronically biased push-pull systems (see Review below). The authors have found that rhodium catalysts bearing sterically hindered acetate ligands such as triphenylacetates are competent catalysts for the intermolecular cyclopropanation of various alkenes. In most cases, the reaction was completely diastereoselective.